Dimming Level Switch Failure

Monitored & Set Condition

1. When Monitored: Continuously.
2. Set Condition: The BCM detects an open or short circuit condition for 10 seconds on the panel lights dimmer signal circuit.

Possible Causes:

• Checking Dimming Switch Positions
• Headlight Switch - Open
• Headlight Switch - Shorted
• Open Headlight Switch Return Circuit
• Panel Light Dimmer Signal Circuit Shorted To Ground
• BCM - Headlight Return Circuit Open
• Measure The Voltage Of The Panel Light Dimmer Signal Circuit
• Open Panel Light Dimmer Signal Circuit
• Panel Light Dimmer Signal Circuit Shorted To The Headlight Switch Return Circuit
• Panel Light Dimmer Signal Circuit Shorted To Voltage

Testing

1. Turn ignition off. Connect scan tool to Data Link Connector (DLC). Using scan tool, read DIMMING LEVEL voltage. If voltage is 0.2-4.0 volts, go to next step. If voltage is not 0.2-4.0 volts, go to step  3 .
2. Turn ignition on. Using scan tool, select BODY COMPUTER, then SENSORS. Observe DIMMING LEVEL voltage while slowly rotating dimmer switch from low to high, then from high to dome. Voltage should increase from 0.6 volt to 5.5 volts, then from 5.5 volts to 9.4 volts. If voltage is not as specified, replace headlight switch. If voltage is as specified, fault may be intermittent. Check related wiring and connectors for poor connections or damage to wiring harness. See WIRING DIAGRAMS  . Repair any problems found as necessary. If no problems are found, check if any Technical Service Bulletins (TSBs) apply to vehicle. If no TSBs apply, test is complete.
3. Turn ignition on. Using scan tool, read DIMMING LEVEL voltage. If voltage is more than 10.2 volts, go to next step. If voltage is 10.2 volts or less, go to step  9 .
4. Turn ignition off. Disconnect headlight switch connector. Disconnect Body Control Module (BCM) connector C2. Measure resistance of headlight switch return circuit (White wire) between BCM C2 connector terminal No. 19 and headlight switch connector terminal No. 6. See Figure and Figure . If resistance is less than 5 ohms, leave connectors disconnected and go to next step. If resistance is 5 ohms or more, repair open in White wire.
5. Measure resistance of panel lights dimmer signal circuit (Red wire) between BCM C2 connector terminal No. 21 and headlight switch connector terminal No. 3. If resistance is less than 5 ohms, leave connectors disconnected and go to next step. If resistance is 5 ohms or more, repair open in Red wire.
6. Turn ignition on. Connect a 12-volt test light between ground and headlight switch connector terminal No. 3, panel lights dimmer signal circuit (Red wire). If test light illuminates, repair short to voltage in Red wire. If test light does not illuminate, leave headlight switch connector disconnected and go to next step.
7. Turn ignition off. Reconnect BCM connector C2. Turn ignition on. Measure voltage on headlight switch connector terminal No. 3, panel lights dimmer signal circuit (Red wire). If voltage is more than 10 volts, leave headlight switch connector disconnected and go to next step. If voltage is 10 volts or less, replace BCM. See BODY CONTROL MODULE  under REMOVAL & INSTALLATION.
8. Connect a jumper wire between headlight switch connector terminal No. 3, panel lights dimmer signal circuit (Red wire) and terminal No. 6, headlight switch return circuit (White wire). Using scan tool, read DIMMING LEVEL voltage. If voltage is less than one volt, replace headlight switch. If voltage is one volt or more, replace BCM. See BODY CONTROL MODULE  under REMOVAL & INSTALLATION.
9. Turn ignition off. Disconnect Body Control Module (BCM) connector C2. Disconnect headlight switch connector. Measure resistance between ground and BCM connector C2 terminal No. 21, panel lights dimmer signal circuit (Red wire). See Figure . If resistance is less than 100 ohms, repair short to ground in Red wire. If resistance is 100 ohms or more, leave connectors disconnected and go to next step.
10. Measure resistance between BCM connector C2 terminals No. 19, headlight switch return circuit (White wire) and No. 21, panel lights dimmer signal circuit (Red wire). If resistance is less than 100 ohms, repair White wire for short to Red wire. If resistance is 100 ohms or more, leave headlight switch connector disconnected and go to next step.
11. Connect BCM connector C2. Turn ignition on. Measure voltage on headlight switch connector terminal No. 3, panel lights dimmer signal circuit (Red wire). See Figure . If voltage is more than 10 volts, replace headlight switch. If voltage is 10 volts or less, replace BCM. See BODY CONTROL MODULE  under REMOVAL & INSTALLATION.